diff options
Diffstat (limited to 'webmap-download')
| -rwxr-xr-x | webmap-download | 235 |
1 files changed, 235 insertions, 0 deletions
diff --git a/webmap-download b/webmap-download new file mode 100755 index 0000000..39c48c2 --- /dev/null +++ b/webmap-download @@ -0,0 +1,235 @@ +#!/usr/bin/python3 + +from os import O_RDONLY, O_WRONLY, O_CREAT, O_TRUNC, O_CLOEXEC, O_PATH, O_DIRECTORY, O_TMPFILE +import os, sys +from fcntl import flock, LOCK_EX +import logging +from time import time, monotonic as time_monotonic +import argparse +import itertools +from pathlib import Path +from email.utils import parsedate_to_datetime, formatdate +from hashlib import sha1 +from math import modf +import requests + +import common + +def download_trystream(url, **kwargs): + max_tries = 10 + f = kwargs.pop('session', requests) + for i in itertools.count(1): + try: + r = f.get(url, **kwargs, stream=True) + except (requests.Timeout, requests.ConnectionError): + if i < max_tries: + logging.error('timeout') + continue + raise + else: + r.raise_for_status() + return r + +def download(url, dest, dir_fd=None, headers={}, max_size=None, session=requests): + logging.info('Downloading %s…', url) + destPath = Path(dest) + dest_tmp = destPath.with_stem(f'.{destPath.stem}.new').as_posix() + try: + # delete any leftover + os.unlink(dest_tmp, dir_fd=dir_fd) + except FileNotFoundError: + pass + + start = time_monotonic() + r = download_trystream(url, headers=headers, session=session, timeout=30) + if r.status_code == requests.codes.not_modified: + # XXX shouldn't we call os.utime(dest) to bump its ctime here? + # otherwise we'll make several queries and get multiple 304 + # replies if the file is used by multiple layers + logging.info('%s: %d Not Modified', dest, r.status_code) + return + + last_modified = r.headers.get('Last-Modified', None) + if last_modified is not None: + try: + last_modified = parsedate_to_datetime(last_modified) + last_modified = last_modified.timestamp() + except ValueError: + logging.exception('Could not parse Last-Modified value') + last_modified = None + + # XXX we can't use TemporaryFile as it uses O_EXCL, cf. + # https://discuss.python.org/t/temporaryfile-contextmanager-that-allows-creating-a-directory-entry-on-success/19094/2 + fd = os.open(os.path.dirname(dest), O_WRONLY|O_CLOEXEC|O_TMPFILE, mode=0o644, dir_fd=dir_fd) + with os.fdopen(fd, mode='wb') as fp: + size = 0 + for chunk in r.iter_content(chunk_size=2**16): + size = size + len(chunk) + if max_size is not None and size > max_size: + raise Exception(f'Payload exceeds max-size ({max_size})') + fp.write(chunk) + r = None + end = time_monotonic() + + # XXX unfortunately there is no way for linkat() to clobber the destination, + # so we use a temporary file; it's racy, but thanks to O_TMPFILE better + # (shorter race) than if we were dumping chunks in a named file descriptor + os.link(f'/proc/self/fd/{fp.fileno()}', dest_tmp, + dst_dir_fd=dir_fd, follow_symlinks=True) + + # no need to close fd here, it was taken care of by the context manager above + + try: + if last_modified is not None: + # XXX os.utime() doesn't work on file descriptors so we set mtime + # after linkat() instead + os.utime(dest_tmp, times=(last_modified, last_modified), + dir_fd=dir_fd, follow_symlinks=False) + os.rename(dest_tmp, dest, src_dir_fd=dir_fd, dst_dir_fd=dir_fd) + + elapsed = end - start + logging.info("%s: Downloaded %s in %s (%s/s)", dest, format_bytes(size), + format_time(elapsed), format_bytes(int(size/elapsed))) + except Exception as e: + try: + os.unlink(dest_tmp, dir_fd=dir_fd) + except Exception: + pass + raise e + +def format_bytes(n): + if n < 768: + return f'{n}B' + elif n < 786432: + return f'{n/1024:.2f}kiB' + elif n < 805306368: + return f'{n/1048576:.2f}MiB' + else: + return f'{n/1073741824:.2f}GiB' + +def format_time(s): + fs, s = modf(s) + m, s = divmod(int(s), 60) + h, m = divmod(m, 60) + return f'{h:02d}:{m:02d}:{s + fs:06.3f}' + +if __name__ == '__main__': + logging.basicConfig(format='%(levelname)s: %(message)s', level=logging.INFO) + + parser = argparse.ArgumentParser(description='Download or update GIS layers.') + parser.add_argument('--cachedir', default=None, + help='destination directory for downloaded files (default: .)') + parser.add_argument('--lockdir', default=None, + help='directory for lock files (default: value of --cachedir option)') + parser.add_argument('--debug', action='store_true', help=argparse.SUPPRESS) + parser.add_argument('--exit-code', action=argparse.BooleanOptionalAction, + help='whether to exit with status 1 in case of download failures') + parser.add_argument('groupname', nargs='*', help='Group(s) to process') + args = parser.parse_args() + + if args.debug: + from http.client import HTTPConnection + HTTPConnection.debuglevel = 1 + logging.getLogger().setLevel(logging.DEBUG) + requests_log = logging.getLogger("urllib3") + requests_log.setLevel(logging.DEBUG) + requests_log.propagate = True + + common.load_config(groupnames=None if args.groupname == [] else args.groupname) + + sources = [] + for name, layerdefs in common.config.get('layers', {}).items(): + for layerdef in layerdefs: + sourcedef = layerdef.get('source', {}) + sourcedef['layername'] = name + sources.append(sourcedef) + + # intentionally leave the dirfd open until the program terminates + opendir_args = O_RDONLY|O_CLOEXEC|O_PATH|O_DIRECTORY + destdir_fd = None if args.cachedir is None else os.open(args.cachedir, opendir_args) + lockdir_fd = destdir_fd if args.lockdir is None else os.open(args.lockdir, opendir_args) + + if ((destdir_fd is None and lockdir_fd is None) or + (destdir_fd is not None and lockdir_fd is not None and destdir_fd == lockdir_fd)): + lockdir_is_destdir = True + else: + destdir_st = os.fstat(destdir_fd) + lockdir_st = os.fstat(lockdir_fd) + lockdir_is_destdir = destdir_st.st_ino == lockdir_st.st_ino + + sessionRequests = requests.Session() + + rv = 0 + downloads = set() + for source in sources: + dl = source.get('download', None) + script = None if dl is None else dl.get('script', None) + if script is not None and script != os.path.basename(__file__): + logging.info('Layer "%s" is not for us (%s != %s), skipping', + source['layername'], + script, os.path.basename(__file__)) + continue + + url = None if dl is None else dl.get('url', None) + if url is None: + logging.error('Layer "%s" has no source URL, ignoring', + source['layername']) + continue + + cache = source.get('cache', None) + dest = None if cache is None else cache.get('path', None) + if dest is None: + raise Exception('Impossible') + elif url in downloads: + logging.info('%s was already downloaded, skipping', dest) + continue + + headers = {} + user_agent = common.config.get('User-Agent', None) + if user_agent is not None: + headers['User-Agent'] = user_agent + dest = str(dest) # convert from Path() + + try: + # create parent directories + destdir = os.path.dirname(dest) + common.makedirs(destdir, mode=0o755, dir_fd=destdir_fd, exist_ok=True, logging=logging) + + # place an exclusive lock on a lockfile as the destination can be used by other layers + # hence might be updated in parallel + if lockdir_is_destdir: + lockfile = dest + '.lck' + else: + # use a flat hierarchy when lockdir != destdir as this avoids leaving empty directories + # behind when removing left overs with tmpfiles.d(5) + lockfile = sha1(dest.encode('utf-8')).hexdigest() + '.lck' + # use O_TRUNC to bump lockfile's mtime + lock_fd = os.open(lockfile, O_WRONLY|O_CREAT|O_TRUNC|O_CLOEXEC, mode=0o644, dir_fd=lockdir_fd) + try: + logging.debug('flock("%s", LOCK_EX)', lockfile) + flock(lock_fd, LOCK_EX) + try: + st = os.stat(dest, dir_fd=destdir_fd) + except (OSError, ValueError): + # the file doesn't exist, or stat() failed for some reason + pass + else: + max_age = cache.get('max-age', 6*3600) # 6h + if max_age is not None: + s = max_age + max(st.st_ctime, st.st_mtime) - time() + if s > 0: + logging.info('%s: Too young, try again in %s', + dest, format_time(s)) + continue + headers['If-Modified-Since'] = formatdate(timeval=st.st_mtime, localtime=False, usegmt=True) + max_size = dl.get('max-size', 2**26) # 64MiB + download(url, dest, dir_fd=destdir_fd, max_size=max_size, + headers=headers, session=sessionRequests) + downloads.add(url) + finally: + os.close(lock_fd) + except Exception: + logging.exception('Could not download %s as %s', url, dest) + if args.exit_code: + rv = 1 + exit(rv) |